For this, I decided to look into Chernobyl. At the Chernobyl nuclear power plant, the
number 4 reactor exploded. This occurred due to a power surge, which happened
because of a design error while trying to shut down the reactor. This led to a huge
nuclear fallout, which evacuated 68000 people. The operators of the reactor decided to
run the reactor at a very low power in which the design was very unstable. The system
involved these rods, which had a graphite section that displaced water and led to an
increase in reactivity, which was what caused the power surge and eventually the whole
disaster to occur.